/****************************************************************************
 * net/bluetooth/iob/iob_trimhead.c
 *
 *   Copyright (C) 2014, 2017 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <assert.h>
#include <debug.h>

#include <tinyara/bluetooth/iob/iob.h>

#include "iob.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#ifndef NULL
#define NULL ((FAR void *)0)
#endif

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: iob_trimhead
 *
 * Description:
 *   Remove bytes from the beginning of an I/O chain.  Emptied I/O buffers
 *   are freed and, hence, the beginning of the chain may change.
 *
 ****************************************************************************/

FAR struct iob_s *iob_trimhead(FAR struct iob_s *iob, unsigned int trimlen)
{
	uint16_t pktlen;

	iobinfo("iob=%p trimlen=%d\n", iob, trimlen);

	if (iob && trimlen > 0) {
		/* Trim from the head of the I/IO buffer chain */

		pktlen = iob->io_pktlen;
		while (trimlen > 0 && iob != NULL) {
			/* Do we trim this entire I/O buffer away? */

			iobinfo("iob=%p io_len=%d pktlen=%d trimlen=%d\n", iob, iob->io_len, pktlen, trimlen);

			if (iob->io_len <= trimlen) {
				FAR struct iob_s *next;

				/* Decrement the trim length and packet length by the full
				 * data size.
				 */

				pktlen -= iob->io_len;
				trimlen -= iob->io_len;

				/* Check if this was the last entry in the chain */

				next = iob->io_flink;
				if (next == NULL) {
					/* Yes.. break out of the loop returning the empty
					 * I/O buffer chain containing only one empty entry.
					 */

					DEBUGASSERT(pktlen == 0);
					iob->io_len = 0;
					iob->io_offset = 0;
					break;
				}

				/* Free this entry and set the next I/O buffer as the head */

				iobinfo("iob=%p: Freeing\n", iob);
				(void)iob_free(iob);
				iob = next;
			} else {
				/* No, then just take what we need from this I/O buffer and
				 * stop the trim.
				 */

				pktlen -= trimlen;
				iob->io_len -= trimlen;
				iob->io_offset += trimlen;
				trimlen = 0;
			}
		}

		/* Adjust the pktlen by the number of bytes removed from the head
		 * of the I/O buffer chain.
		 */

		iob->io_pktlen = pktlen;
	}

	return iob;
}
